Local authorities: a source of organic waste and a way of recovering heat for agricultural methanisation ?

Abstract

In order to increase profits, all on-farm anaerobic digestion (AD) needs (i) waste with a high capacity to produce methane and (ii) an economic valorization of the heat produced. This article shows that local authorities produce a large amount of organic waste, like waste from restaurants, the organic fraction from household refuse, urban sludge, green algae. Despite this diversity, only few sources can be used for on-farm AD because the waste must have a high methanogenic potential, be sorted, stored within a close distance and have the possibility of payments in royalty fees: those factors are difficult to combine. However, there are examples, evidence of opportunities and margins for progress. At the same time, local authorities have many buildings, which sometimes have very high thermic needs and hot water consumption. The added value of thermic energy produced by anaerobic digestion sometimes faces constraints, such as distance and urban density, which create high costs for heating networks. Opportunities of partnership between on-farm biogas production and local authorities are real but need to be studied on an individual case basis.